Magnet core



Patented Oct. 31, 1933 UNITED STATES MAGNET CORE Philip Norton Roseby,Liverpool, England, as-

signor to Automatic Electric Company Limited,

Liverpool, England No Drawing. Application July 27, .1932, Serial No.

625,208, and in Great Britain July 30, 1931 7 Claims.

The present invention relates to the construction of magnet cores and isparticularly concerned with the manufacture of cores of the type madefrom powdered material by the applicaticn of high pressure which findconsiderable application in loading coils as applied to a telephonetransmission line. The object 01 the invention is to produce an improvedcore of this type by the use of a special alloy and also by 10 the useof an insulating film with more satisfactory properties than thoseemployed hitherto.

According to one feature of the invention, the magnetic particles fromwhich the core is pressed consist of an alloy of iron,nickel and cobalt,for instance in the proportions of 60% iron, nickel and 20% cobalt, or60% iron, nickel and 15% cobalt.

According to another feature of the invention the insulating film whichis necessary to separate the particles from one another consists whollyor mainly of a metallic fluoride which has the valuable property thatits insulating qualities are not impaired by the heat treatment whichwith the alloy considered is desirable after press- 25 ing and also thatit is able to withstand satisiactorily the high pressures employed informing the coil.

In order that the invention may be better understood a description willbe given of a preferred method of carrying it into effect which isgenerally similar to that described in my patent specification No.1,850,181 in connection with a nickel-iron alloy. According to thisprocess, an alloy of iron, nickel and cobalt in the proportions of 60%,20% and 20% or 60%, 25% and 15% is drawn out into wire of a diameter ofthe order of 4 mils, and this is then chopped into small lengths, forinstance in". The chopped wire is heated to a temperature ofapproximately 900 C., and is then cooled in air moderately quickly, forinstance by distributing it on a copper plate. The wire particles arethen placed in a rotating metal drum with sufficient hydrofiuoric orhydrofiuosilicic acid solution to wet the particles. Heat is applied andthe temperature is gradually'raised to approximately 300 C. whereuponthe chemical reaction which takes place is substantially complete andthe particles are then coated with a film consisting wholly or mainly ofmetallic fluoride. The particles are now mixed with a suitable quantityof a binder, for instance powdered magnesia, are subjected to a magneticalignment process for instance as described in my application Serial No.498,694 filed 28th November 1930, and are pressed in a ring mould. Afterthe pressing operation the cores are heated to a temperature of 450-500C. which operation serves to increase considerably the permeability ofthe cores and to reduce 60 the hysteresis loss.

It may be mentioned that the percentages given above for the compositionof the alloy are only approximate and also that in some circumstances itmay be desirable to add a small percentage of an element such assilicon, tantalumor chromium in order to increase the specificresistance.

What I claim as new and desire to secure by Letters Patent is:

1. A magnet core for loading coils or the like in which the finelydivided magnetic particles from which the core is pressed are separatedfrom one another by a coating of metallic fluorides.

2. A process for making magnet cores for loading coils or the like inwhich finely divided particles of an alloy of iron, nickel and cobaltare treated with hydrofluosilicic acid and subsequently subjected tohigh pressure.

3. A process for making magnet cores for loading coils or the like inwhich finely drawn wire of an alloy comprising approximately iron, 20%nickel and 20% cobalt is chopped into small lengths and treated withhydrofiuosilicic acid and subsequently subjected to high pressure.

4. A process for making magnet cores for loading coils in which finelydrawn wire of an .alloy comprising approximately 60% iron, 20%

nickel and 20% cobalt is chopped into small lengths, heated toapproximately 900 C. and after cooling treated with hydrofluoric acidwith gradually increasing temperature up to approximately 300 C. afterwhich the particles are mixed with a. binder such as powdered magnesiasubjected to a magnetic aligning process pressed to cause them toagglomerate and subsequently heated to a temperature of approximately500 C. to improve the magnetic properties of the resulting core.

1 5. A process for making magnet cores for loading coils or the like inwhich finely divided particles of an alloy of iron, nickel and cobaltare treated with hydrofluoric acid and subsequently subjected to highpressure.

6. A process for making magnet cores for loading coils or the like inwhich finely drawn wire of an alloy comprising approximately 60% iron,20% nickel, and 20% cobalt is chopped into small lengths and treatedwith hydrofluoric acid and subsequently treated to high pressure.

7. A process for making magnet cores for loading coils or the like inwhich finely drawn wire of an alloy comprising approximately 60% iron,20% nickel, and 20% cobalt, to which is added a small proportion of anelement to increase the specific resistance, is chopped into smalllengths, treated with hydrofluoric acid and subsequently subjected tohigh pressure.

PHILIP NORTON ROSEBY.

